Contributo alla conoscenza della Flora dei pascoli erbosi e boschivi di Monterotondo (Roma)

Summary

After having summarly described the ecological conditions of the area of the Roman Province which are studied by the author, he lists the plants collected and adds some critical remarks on the taxonomy. He gives a list of a few taxa, which must be regarded as having been found for the first time in Lazio, or are infrequent in this Province.

The author describes the vegetation of some pastures and woods by means of statistical investigations. Finaly he takes into consideration the reciprocal influence exerted by the various plant-communities.     

Trinia Dalechampii Janch. et W. Nel Componente Illirico della Flora Apuana di Altitudine

Abstract

TRINIA DALECHAMPII in the Illyric component of the Flora of the Apuan Alps. — On a mountaintop in the Apuan Alps, the author found Trinia dalechampii, an Illyric entity known until now in Ytaly only in the central and southern Apennines. He also indicates that a Greco-Apennine Oligo-Miocene bridge was the probable migration-route of this species and likewise of the Illyric entities of the Apennines.     

Sul ricambio gassoso della uova di bachi da seta (Bombyx mori L). II

Riassunto Sono stati eseguiti esperimenti col metodo manometrico diwarburg sulla respirazione delle uova annuali (bianco cinese, giallo indigene) e bivoltine 2^o generazione (Awoiko) nel periodo di incubazione dal 14 aprile al 5 maggio.L'intensitá respiratoria delle uova di tutte le tre categorie aumenta continuamente finche raggiunge il suo massimo colla nascita dei bacolini.Ho distinto nello sviluppo delle uova sulla base dell' attivitá respiratoria dalla deposizione delle uova fino alla nascita dei bacolini tre periodi: Nel primo periodo l'intensitá respiratoria aumenta continuamente fino a raggiungere un massimo, questo primo periodo dura 4 o 5 giorni.Nel secondo periodo T intensitá respiratoria si abbassa notevolmente e rimane nei limiti bassi durante alcuni mesi, solo in primavera l'intensitá respiratoria s' inalza e raggiunge in fine il livello della intensitá raggmnta nel primo periodo. Questo periodo e la diapausa.Nel terzo periodo (incubazione) l' intensitá respiratoria cresce coninuamente raggiungendo il massimo colla nascita dei bacolini.Se noi sommiamo i giorni del continuo aumento della intensitá respiratoria ossia quello del primo e del terzo periodo, escluso il secondo periodo, avvremo un totale di 10–11 giorni.Ora la prima generazione delle bivoltinc si sviluppa ininterrotamente senza la diapausa, anche per il suo completo sviluppo sono nescessari circa 11 giorni. Dal punto di vista dell' attivitá del ricambio gassoso sembra ehe nel lungo periodo di diapausa non avvengono fenomeni di accrescimento, bensi avvengono dei processi di natura ignota.

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Zusammenfassung Es wurden nach der manometrischen Methode vonWarburg Untersuchungen gemacht über die Atmung von Eiern der Seidenraupe annuali (bianco cinese und giallo indigene), bivoltine 2. Generation (Awoiko). Die Versuche wurden in der Zeit vom 14. April bis 5. Mai, die Zeit der Inkubation, ausgeführt. Die Intensität der Atmung stieg kontinuierlich bei den Eiern aller drei Kategorien, bis sie ihren Höhepunkt mit dem Ausschlüpfen der Raupe erreichte.Bezüglich der Atmungsaktivität wurden in der Entwicklung des Eies von seiner Ablage bis zur Geburt der Raupe drei Perioden unterschieden:In der ersten Periode stieg die Atmungsintensität kontinuierlich an bis zur Erreichung eines Maximum. Diese Periode dauert 4 bis 5 Tage.In der zweiten Periode sinkt die Atmungsintensität allmählich und bleibt auf einer ziemlich niedrigen Stufe konstant. Nur im Frühling steigt sie wieder an, bis sie das Niveau erreicht, das sie bereits in der ersten Periode gehabt hat. Diese Periode sei als Diapausa bezeichnet.In der dritten Periode (Inkubation) steigt die Atmungsintensität kontinuierlich bis zu ihrem Höhepunkt bei dem Ausschlüpfen der Larve.Wenn wir die Summe der Tage mit kontinuierlichem Ansteigen der Atmungsintensität betrachten, d. h. die Summe der Tage in der ersten und dritten Periode unter Ausschließung der zweiten Periode, so erhalten wir eine Summe von 10 bis 11 Tagen. Es ist bemerkenswert, daß die Entwicklung der Eier der ersten Generation der bivoltine, die kontinuierlich ohne Diapausa abläuft, ebenfalls 11 Tage dauert.Vom Standpunkte der Aktivität des Gasstoffwechsels aus scheint es, daß in der langen Periode der Diapausa keine Entwicklungserscheinungen vorhanden sind; man muß vielmehr Prozesse unbekannter Natur annehmen.

     

Evoluzione Annuale della Cerchia Legnosa in Individui Maschili E Femminili di Ginkyo Biloba L.

Abstract

Wood ring evolution in male and female plants of GINKYO BILOBA L. — A morphological examen of the wood rings in Ginkyo biloba L. has been performed on stem sections from specimens of the Botanical Institute of Florence, on wood samples from the collection of Adriano Fiori and on wood cores extracted from the stem of male and female plants growing in the Botanical Garden of Florence.

At the same time the development of the growth ring has been followed on wood samples tacken off the stems of two adult Ginkyo plants growing in the Botanical Garden of Florence.

All the material which has been studied shows the same characters, that is the frequency of uncomplete crescent-shaped wood rings, and consequently a large degree of eccentricity of the stems, depending not only upon the uncomplete wood rings, but also on the changing width of each ring.

Microscopical analysis has pointed out the presence of false rings, limited by discontinuous late wood, particularly in the female plant. This character has been observed only in a fossil wood of Ginkyo bonesii.

It has not been possible to assers how many rings or crescents are formed during one year. From dating records made on wood cores it seems that more than one ring could differentiate during one year, but the cambium shows a very irregular activity in Ginkyo. The factors which control the formation of false and uncomplete wood rings (wood crescents) are also unknown; their formation possibly depending upon environment conditions.

External factors such as water deficiency probably control cambial activity through auxin production. Larson (1964) has shown that draught causes a decrease in tracheids diameter, and the formation of false growth rings; thus the same causes could have been in action in our plants.

Noteworthy are also the data by Gungkel and Thimann (in Larson 1964) showing that auxin content increases downwards in the shoots of Ginkyo and that the apical bud has a very low auxin production, so that it seems possible that in Ginkyo the leaves supply something which the cortical tissue converts into auxin.

Lastly, the almost continuous growth activity of the cambium in Ginkyo must be pointed out, this causes a great difficulty in checking the beginning and the end of this process along the year. It is any way possible to establish the time of the highest cambial activity, which lies in June-July both in the female and in the male plants.     

Ultrastruttura della cellula apicale di Halopteris scoparia (L.) Sauvageau (Phaeophyceae,Sphacelariales)

Abstract

Ultrastructure of the apical cell of Halopteris scoparia (L.) Sauvageau (Phaeophyceae, Sphacelariales). - The ultrastructure of resting apical cells of Halopteris scoparia (L.) Sauvageau from material collected in December is described. The cytoplasm is higly vacuolated with lipids, poliphenolic substances and polisaccharides occurring inside the vacuoles (the classic « physodes »).

Two cell organelles are prominently active at this stage: conspicuosly hypertrophic dictyosomes and the budding endoplasmic reticulum. Both light and electron microscope observations show that the cell wall has an outer stratification and inner discontinuous thickenings, the constituent material of which is uniformerly dispersed.

The above observations point out that the apical cell of Halopteris scoparia at this stage of its life cycle is engaged in an elaboration of vacuolar and parietal substances which will be therefore readly available at the outset of the growing season.     

L'evoluzione della cerchia legnosa in Quercus Pubescens W. Ein Quercus Ilex L. nel clima di Firenze

Summary

The evolution of the wood ring in Quercus pubescens W. and in Quercus Ilex L. in Florence (from June 1946 to June 1947).

The present study deals with the anatomical characters of the wood ring of Q. pubescens and of Q. Ilex. In both the specimens the wood of the stem and of the young branch has been investigated.

In both plants studied the cambial tissue of the stem starts dividing at the end of April, reaching its maximum activity from May to June.

On the contrary the cambium of the branch differentiates in Q. pubescens a month earlier (18 March-18 April) than in Q. Ilex (18 April-18 May). While in the branch of Q. Ilex a false ring can be seen corresponding to the autumn months, nothing of the kind is found in the branch of Q. pubescens; though it presents a false ring in the stem.

It is difficult to date clearly the period when the cambium stops its activity, but probably it happens at the end of August in the samples of the stem.

The leaf buds of Q. pubescens and of Q. Ilex open during April-May and the young branch is completely developed at the end of June. In both oaks some buds open in autumn, but the small branches are prevented to develop because of the cold.

No comparison can be made between the opening of the buds and the beginning of the cambial activity in the stem and in the branch.

Considering the evolution of these woods and their relationship to climatic factors, we can see that the cambial activity starts during a period of remarkable rainfall and of regular increase of temperature, and stops almost completely at the end of July, when temperature and dryness reach their highest values.

The autumn rainfall would favour again a cambial activity, but the values of the temperature, regularly decreasing, do not allow it.     

Ulteriori ricerche sulla germinazione di Cercis siliquastrum L. Azione dell'acido gibberellico e ruolo dell'endosperma nel fenomeno della dormienza

Abstract

Further research on the germination of Cercis siliquastrum L. Effect of gibberellic acid (GA₃) and role of endosperm in dormancy.—In order to locate the causes of the dormancy in Cercis siliquastrum L., researches have been carried out also on non-scarified seeds without integument, as well as on isolated embryos.

We have noted that gibberellic acid can substitute the cold treatment to interrupt the dormancy and we have also investigated the optimal concentrations.

The results we have obtained do not show the inhibition to be located in the integument and point out a determinant role of the endosperm.

Histological investigations are being carried out to study better the possible occurrence of a mechanical restraint imposed by the albumen on the non-dormant embryo.